The present invention relates to surface treating articles and to a method for the manufacture of such articles.
Surface treating articles such as flap brushes, cleaning brushes, bristle brushes and convolute wheels are known. Exemplary of these surface treating articles are those available from the Minnesota Mining and Manufacturing Company of St. Paul, Minn. under the trade designation xe2x80x9cScotch-Britexe2x80x9d. Flap brushes include a central core with a plurality of compressed radially extending strips or flaps of abrasive-containing nonwoven material. An edge of each flap is attached to the core while the opposing free edges of the compressed flaps form the outer working surface of the brush. Surface conditioning operations with these articles are accomplished by rotating the core while the working surface of the article is maintained in contact with a workpiece. Flap brushes may be used, for example, in the surface preparation and conditioning of metals, woods, plastics and other materials to prepare the surfaces for painting, plating, or the like as well as to impart a desired finish to the surface of a workpiece. The construction of other surface treating articles such as cleaning brushes, bristle brushes, convolute wheels and the like is similar to the aforementioned flap brushes in that all of these articles are made by attaching suitable surface treating segments such as flaps, discs or bristles, for example, to the outer peripheral surface of a rotatable core.
In the aforementioned articles, attachment of surface treating segments to a core may be accomplished by mechanical means and/or with a suitable adhesive. Although known mechanical attachments are relatively simple in their construction, they add weight to the finished article which, in turn, can cause rotational balancing problems in use. Additionally, the inclusion of mechanical attachments in the manufacture of surface treating articles can complicate manufacturing processes. Because of these difficulties, adhesives have been extensively employed as alternatives to mechanical fasteners in the manufacture of the foregoing articles.
Although the use of adhesives has been successful in overcoming many of the problems associated with mechanical attachments, other problems have arisen. A significant problem has been the formation of void spaces in the adhesive. To provide a strong adhesive bond resistant to failure during normal brush operation under high rotational forces, the bond line between the core and each of the surface treating segments must be substantially continuous (e.g., with no significant voids in the adhesive to serve as stress risers). In practice, however, voids of significant volume frequently occur within the core/segment bond line which, in turn, can result in a weakened bond that may cause adhesive failure when the finished article is later used. Moreover, such voids in the cured adhesive are difficult to detect due to the overall size of many surface treating articles. For example, depending on the intended use of the finished article, abrasive articles such as flap brushes and the like are manufactured to have a significant width (e.g., 0.5 meter or more), making an adequate inspection of the adhesive bond line between the core and the individual segments difficult at best. Accordingly, it is desirable to provide surface treating articles such as flap brushes, cleaning brushes, bristle brushes, convolute wheels and the like wherein the surface treating segments are attached to the core with an adhesive and wherein the adhesive is effective in forming a strong core/segment interface substantially free of objectionable void spaces.
Aside from the above described concerns relating to mechanical failure, additional aesthetic concerns are raised by the formation of voids in the core/segment interface. In the manufacture of the flap brushes, for example, the manufactured brush is often cut to a smaller size for certain applications. Cutting the manufactured article exposes a new portion of the core/segment interface that may or may not have a uniform and concentric adhesive bond line. The presence of visible void spaces in the adhesive interface may be considered undesirable for aesthetic reasons. Accordingly, it is desirable to provide surface treating articles such as flap brushes, cleaning brushes, bristle brushes, convolute wheels and the like wherein an adhesive is used in the attachment of the surface treating segments to the core and wherein the adhesive provides a strong and aesthetically acceptable interface between the segments and the core.
Efforts have been made to solve the problem of adhesive failure by making mechanical modifications to the construction of the core, for example, to promote the uniform application of adhesive over the core. Although these efforts have met with some success, it is desirable to provide a solution to the aforementioned problem without the need to substantially modify the mechanical components of the aforementioned surface treating articles. It is desirable to provide surface treating articles such as flap brushes, cleaning brushes, bristle brushes, convolute wheels and the like wherein an adhesive is used in the attachment of the surface treating segments to the core and wherein the adhesive is expansive in a molten or fluid state so that, when the surface treating segments are applied to the core member, the adhesive will expand into and around the segments to form a strong bond between the core member and the abrasive segments and wherein the expanded adhesive is substantially free of significant void spaces.
The present invention provides surface treating articles such as flap brushes, cleaning brushes, convolute wheels and the like wherein the abrasive or surface treating segments of the article are affixed to a rotatable core with an expansive adhesive. The adhesive used in the articles of the present invention is applied to the core during the manufacturing process, and surface treating segments are then applied to the adhesive on the core. The adhesive is expanded (e.g., by heating) into and around a portion of each the surface treating segments and the adhesive is hardened (e.g., by curing at elevated temperatures) to provide a core/segment bond line which is strong and substantially free of significant voids.
In one aspect, the present invention provides a surface treating article comprising:
a rotatable core having an outer surface;
a plurality of surface treating segments, each said segment having first portions adjacent said outer surface of said core and second portions opposite said first portions, said second portions collectively arranged to form a working surface of the surface treating article; and
a cured expanded adhesive composition bonding said first portions of said surface treating segments to said outer surface of said core.
The core provides a locus for the attachment of the surface treating segments and preferably is a tube, rod, beam, pipe, or the like which may have a central bore therethrough. The core may include protrusions extending from the outer surface or it may have indentations along the outer surface, or a combination of protrusions and indentations. Surface treating segments useful in the articles of the invention include those comprising woven, nonwoven or knitted fabrics, foamed compositions (open or closed cell), flexible molded compositions and the like. The segments are preferably coated with a suitable binder and may include abrasive particles. Individual surface treating segments may be provided, for example, in the form of rolls, sheets, strips, annuli, discs, bristles, filaments, yarns, paper or polymeric film or any other form suitable for the manufacture of a particular abrasive article.
In a particularly preferred embodiment within this aspect if the invention, the cured expanded adhesive composition comprises the reaction product of:
a) an organic epoxide compound having an epoxide functionality of at least 1,
b) an epoxide hardener,
c) a film-forming material, and
d) a foaming agent.
Accordingly, the cured adhesive preferably comprises a foamed organic epoxide which has been expanded into and around the edge of the segments adjacent the core. The organic epoxide preferably has an epoxide functionality between 2 and 4, and the epoxide hardener is preferably a mixture of dicyandiamide and 2,4-di-(Nxe2x80x2,Nxe2x80x2-dimethylureido)toluene.
As used herein, xe2x80x9csurface treating articlexe2x80x9d means any of a variety of articles useful in the treatment of surfaces including without limitation flap brushes, cleaning brushes, bonded wheels, bristle brushes and the like. xe2x80x9cSurface treating segmentxe2x80x9d broadly means materials which can be affixed to a rotatable core to form a surface conditioning article including those specific materials described herein. xe2x80x9cExpansive adhesive compositionxe2x80x9d means an uncured adhesive formulation capable of volume expansion by heating or the like. xe2x80x9cCured, expanded adhesivexe2x80x9d or xe2x80x9ccured adhesivexe2x80x9d refers to an expansive adhesive composition which has undergone volume expansion and hardening (e.g., by heat curing). xe2x80x9cEpoxide hardenerxe2x80x9d means curing agents, catalysts, epoxy curatives, and other curatives useful for curing epoxy resins.
In another aspect, the invention comprises a method for the manufacture of a surface treating article comprising:
a) applying an expansive adhesive composition to the outer periphery of a rotatable core, said adhesive composition comprising:
i) an organic epoxide compound having an epoxide functionality of at least 1,
ii) an epoxide hardener,
iii) a film-forming material, and
iv) a foaming agent;
b) providing a plurality of surface treating segments having first portions thereon suitable for positioning adjacent said core, and second portions which can be collectively arranged to form a working surface of the surface treating article;
c) applying said plurality of surface treating segments to said core by positioning said first portions adjacent said core and in contact with said adhesive;
d) expanding said expanded adhesive about said first portions of said surface treating segments; and
e) hardening said adhesive to form the surface treating article.
In this aspect of the invention, the core and surface treating segments are as described in the first aspect of the invention. The application of the expansive adhesive to the core may be accomplished by applying the adhesive as an uncured paste or a film which can be expanded after its application. The preferred adhesive is one which will experience low sag and low volatile loss during cure, has high shear strength (tube shear and flexural shear) after cure and will readily bond to both the core and the surface treating segments. The application of the surface treating segments is accomplished in a manner suitable for the particular type of segments being used, as further described herein. Preferably, the adhesive can be both expanded and cured by the application of heat.
Those skilled in the art will further understand and appreciate the details of the invention upon the further consideration of the remainder of the disclosure, including the detailed description of the preferred embodiment and the appended claims.